Candidate release 1.4.0

[jgriffiths]

Added

• tx: Add caching to signature hash generation/PSBT signing making signing faster.
• tx: Add support for generating Elements taproot signature hashes and signing Elements taproot inputs.
• descriptor: Add support for "tr()/rawtr()" keyspend-only taproot descriptors.
• descriptor: Add support for parsing Elements-core compatible descriptors, including taproot.
• psbt: Add accessors for keypath/taproot related fields.
• pset: Add support for ELIP-101 genesis hash.
• psbt: Add support for serializing/parsing/combining signature-only PSBTs.
• script: Add support for generating Elements p2tr scripts.
• BIP85: Add support for deriving RSA keys via BIP85.
• base64/psbt: Add support for parsing from known length (non-NUL terminated) strings.
• build: Add Debian Bookworm docker build image.

Changed

• tx: Re-implement signature hash generation to use less stack space and CPU independently of caching.
• amalgamation: Provide the amalgamated build as a single source file, make it simpler to use.
• build: CI improvements: New valgrind, scan-build and ubsan/addrcheck/etc builds. Add CI/test runs
  for builds with elements support disabled.
• build: Update/extend tests to make it easier to catch errors in the new CI builds.

Fixed

• psbt: Fix detection of expired CSV inputs for v0 PSBTs.
• psbt: Fix finalization of non-optimized CSV inputs (e.g. Green Liquid 2of2).
• tx: Fix incorrect sighash masking for BTC taproot inputs.
• build: Various fixes and test improvements for non-Elements builds.
• Various minor code and build fixes.